Grounding...I’m genuinely confused now

[ClemsonSCJ]

Alright so I am doing an install on a new mobile vhf/uhf and major overhaul to the wiring on all my current stuff to work out the last of my kinks, or so I thought. I had posted a while back about getting some whine in my CB when I hit the gas really hard which I learned was because I likely had the CB powered by a circuit with a lot of noise and it was recommended to go straight to the battery. Well I did that, but in my limited understanding, only did it on the positive side and not the ground side. I left the ground to a random piece of metal under the dash and although it cleared up most of my whine, I still get it faintly. I also noticed I get a lot of static when I turn my brights and fogs on. Well since then I’ve been reading and learning more (mostly with respect to ham but a lot of the information carries over to CB) and realized the error of my ways and so today as I install my new mobile radio, I was gonna totally redo the grounding for both radios to come straight off the battery.

So there I was cutting wires loose on my CB and when I cut the ground, the CB stayed on. I pulled the antenna cable and it turned off. I plug the antenna back up and radio comes back on. So obviously the grounding from the antenna is proving the ground to the power circuit, which I guess makes sense but it begs the question...even after I ground directly to the battery, am I going to clean up a lot of the static I’m getting, and are those same issues going to carry over to the new vhf/uhf mobile I’m installing?

 

[WA0CBW]

Well....
Depending on the year and make of your vehicle the negative lead of the battery to chassis has a current sending device that monitors the current for battery drain and charging. Connecting the negative lead directly to the battery bypasses this and can cause electrical problems with the cars computer(s).

You should connect the negative lead of the radio directly to the chassis with as short a lead as possible. Alternately the negative lead can be connected to the chassis at the same point where the battery negative lead connects to the chassis.
Bill

 

[KEWB-N1EXA]

I know i'm going to get the wall of FLACK from the big gun on this but ! They cant help themselves !

On My old Isuzu Trooper I ran my power from the battery to the 10 meter ham rig using Coax ( RG58) the power lead was the center ground was the shield.

Got me around the Spark plugs snapping on the radio.

Peter N1EXA

 

[jonwienke]

You probably had significant voltage drop when you keyed up, though...

 

[KEWB-N1EXA]

You probably had significant voltage drop when you keyed up, though...

A Radio Shack HDX 100 is no power house... Worked just fine.
I used stranded core RG-58 Cable I'm sure 2-3 amps was no issue for it.

As they say Puttin Pennies on the track is not going to derail the train !

Pete N1EXA

 

[WB9YBM]

So there I was cutting wires loose on my CB and when I cut the ground, the CB stayed on. I pulled the antenna cable and it turned off.

Even with the CB power switch in the "OFF" position?

 

[ClemsonSCJ]

Even with the CB power switch in the "OFF" position?

No I have my cb to where the switch stays on and it just gets power when I turn the key on. It stays on for 10 min after I turn the key off so I was still in that 10 min window.

 

[wtp]

CB being AM really likes to bring you the static.
going to FM should help.
years ago i have a 'spare' battery in my back seat and would/could /did use it for the CB.
i worked security and would bring in the battery and radio for something to listen to.
i even had my pro2001 wired to it with the CB.

 

[WB9YBM]

going to FM should help.

Well, yes and no. You might not hear the static bursts on FM but on the other hand there's still a noise floor of static which can vary quite a bit depending on atmospheric noise, hash kicked out by electrical systems, etc.

 

[WB9YBM]

No I have my cb to where the switch stays on and it just gets power when I turn the key on. It stays on for 10 min after I turn the key off so I was still in that 10 min window.

Sounds like it might be getting power from some system that becomes active with the ignition key being in the "accessory" or "engine run" position...

 

[ClemsonSCJ]

Sounds like it might be getting power from some system that becomes active with the ignition key being in the "accessory" or "engine run" position...

So the way it works is I have my CB and new mobile dual band powered directly off the battery (which I am in the process of changing both pos and neg to the battery). I have a relay in line with both positives that is triggered by a device that kicks both on when it receives 12V (13V in the case of the dual band since it pulls way more power being 12x the wattage). When voltage drops below those respective thresholds, the device has a set timer (10 min for the CB and 5 min for the dual band) and then it will shut off.

 

[AJAT]

Here is a good article that may explain why your radio stayed on when you lost your ground: Mobile Radio Wiring and Grounding
I have heard the argument both ways, both neg and pos directly off the battery, and only the pos directly off the battery. I would say the consensus from what I heard is it is best for the pos to go directly to the battery, neg goes to the chassis. When I installed my hf/dual band rig I came off the battery directly with both neg and pos. I have no issues, not saying it is right or wrong.

 

[ClemsonSCJ]

Thanks for all the input guys. The job took about 4 hours longer than I thought it would. But everything is about as properly done is I can do it now except for one thing that got jacked up at the very end.

As I’m wrapping up I noticed nothing was getting power. Ended up being something with the relay timer device I was using...I guess it just went bad. Sucks cause apparently they don’t make it anymore (PAC TR-12) and I have scoured the internet over to find something similar and I’m having a hard time so any input on that would be appreciated.

Basically I want the CB to come on when the key is in the run position and the dual band to come on when the vehicle is actually running. When power is cut, I want the dual band to remain on for 5 minutes and the CB to remain on for 10 minutes. The TR12 I was using was computer programmable so I had one input wire set to trigger at 12V for the CB and another to trigger at 13.8V for the dual band. The output wires were programmed to turn on when the trigger reached their set threshold voltage and then then off however many minutes after they went below that threshold voltage.

Anybody know if anyone that makes anything else similar?

 

[AJAT]

You can use a combination of a voltage sensing relay and a time delay relay https://www.amazon.com/NOYITO-Volta...age+sensing+relay&qid=1612492772&sr=8-12&th=1 and

https://www.amazon.com/HELLA-996152...words=time+delay+relay&qid=1612492967&sr=8-13 might work.

You would need 2 each. The voltage sensing relay energizes the time delay relay that has a delay on off. There might be similar products out there that work better for your situation. Combing a voltage sensor relay with a time delay relay should work if you can't find anything else.

 

[mmckenna]

You mentioned you were getting some noise when the headlights and/or fog lights were on.
By chance are the HID or LEDs?

The HID's can be noisy due to the step up converter. Some LED systems are just noisy because they are cheap and poorly made. Incandescent lights won't have that problem. Good LED's won't, either.

As for grounding….
If your CB antenna base is well grounded, it will provide a path for the return to the battery. The shield of the coax connects to the outer conductor of the coax plug. That's connected to the chassis of the radio, which is where the negative power lead is ultimately connected. So, completely normal. You obviously do not want to rely on that, though.

Running your negative power lead all the way back to the battery isn't an issue in itself. You usually want to avoid connecting it directly at the battery as some newer vehicles have a sensor on the negative battery cable that looks at the amount of current leaving/going into the battery to control the charging circuit. Bypassing that by having a grounded antenna connected to a grounded radio and negative lead going back to the battery can cause issues. Modern cars will often have a section in the manual advising against that. It is usually preferred to use one of these methods:

Use the vehicle body as the return path to the negative battery post. Some manufacturers will have a return current limit, however, but it's usually in the 30-40 amp range.​

​

Use a negative power lead back to the point where the negative strap from the battery connects to the vehicle body.​

​

Either way, its a good idea to have a grounding strap from the radio chassis to the vehicle body. A short strap gives an easy place to bleed off any stray energy to the body, without relying on a long run back to the battery or via the antenna mount. If you don't have that, I'd advise adding one. It can fix/prevent some issues that will drive you nuts.

 

[ClemsonSCJ]

You mentioned you were getting some noise when the headlights and/or fog lights were on.
By chance are the HID or LEDs?

The HID's can be noisy due to the step up converter. Some LED systems are just noisy because they are cheap and poorly made. Incandescent lights won't have that problem. Good LED's won't, either.

The regular beams are HID’s, but they are factory. The high beams and fogs are aftermarket HID’s so probably what the issue is. Good to know cause I’ve been contemplating going LED anyways cause the long “warm up” time for the HID high beams makes them almost worthless unless you know there isn’t going to be a car for a while. They are bright as hell though.

As for grounding….
If your CB antenna base is well grounded, it will provide a path for the return to the battery. The shield of the coax connects to the outer conductor of the coax plug. That's connected to the chassis of the radio, which is where the negative power lead is ultimately connected. So, completely normal. You obviously do not want to rely on that, though.

Running your negative power lead all the way back to the battery isn't an issue in itself. You usually want to avoid connecting it directly at the battery as some newer vehicles have a sensor on the negative battery cable that looks at the amount of current leaving/going into the battery to control the charging circuit. Bypassing that by having a grounded antenna connected to a grounded radio and negative lead going back to the battery can cause issues. Modern cars will often have a section in the manual advising against that. It is usually preferred to use one of these methods:

Use the vehicle body as the return path to the negative battery post. Some manufacturers will have a return current limit, however, but it's usually in the 30-40 amp range.​

​

Use a negative power lead back to the point where the negative strap from the battery connects to the vehicle body.​

​

Either way, its a good idea to have a grounding strap from the radio chassis to the vehicle body. A short strap gives an easy place to bleed off any stray energy to the body, without relying on a long run back to the battery or via the antenna mount. If you don't have that, I'd advise adding one. It can fix/prevent some issues that will drive you nuts.

Thanks for that explanation. I’m using a grounding block to have all of my grounds hooked to a common place. The place where I have it is by the framing for the dash. It’s heavy gauge tubing all welded together and just raw steel, nothing painted. Do you think that would be sufficient to ground to rather than the negative battery lead or should I link in to where the negative battery lead is hooked to the chassis?

 

[mmckenna]

Good to know cause I’ve been contemplating going LED anyways cause the long “warm up” time for the HID high beams makes them almost worthless unless you know there isn’t going to be a car for a while. They are bright as hell though.

Yeah, I have HID conversion on my Polaris Ranger. It works well because there are no hi-beams, they are either on or off. They do take a while to warm up, but once they do, it's really bright.

The ones I have were inexpensive when I bought them, probably in the $40 range for the set back when I bought them in 2011. No issues with the VHF radio in there.

I've got an inexpensive LED bar, too, and they've been OK. Actually, haven't had any issues with SuperBrightLEDS.com or the more expensive ones I've purchased. Maybe it has something to do with the install.

Thanks for that explanation. I’m using a grounding block to have all of my grounds hooked to a common place. The place where I have it is by the framing for the dash. It’s heavy gauge tubing all welded together and just raw steel, nothing painted. Do you think that would be sufficient to ground to rather than the negative battery lead or should I link in to where the negative battery lead is hooked to the chassis?

Body/frame ground should be fine for this sort of load. Some manufacturers will specify a maximum amperage for return through the body. On a modern Chevy pickup, it's something like 30 amps worth of add on accessories. Your vehicle may be different. Welded steel should be just fine if you have good connections. Just make sure to protect them so they don't corrode/rust.
If you are running a lot of amperage back through the chassis, you can upgrade the size of the strap running from the battery negative post to the body.

 

[MUTNAV]

Yeah, I have HID conversion on my Polaris Ranger. It works well because there are no hi-beams, they are either on or off. They do take a while to warm up, but once they do, it's really bright.

The ones I have were inexpensive when I bought them, probably in the $40 range for the set back when I bought them in 2011. No issues with the VHF radio in there.

I've got an inexpensive LED bar, too, and they've been OK. Actually, haven't had any issues with SuperBrightLEDS.com or the more expensive ones I've purchased. Maybe it has something to do with the install.



Body/frame ground should be fine for this sort of load. Some manufacturers will specify a maximum amperage for return through the body. On a modern Chevy pickup, it's something like 30 amps worth of add on accessories. Your vehicle may be different. Welded steel should be just fine if you have good connections. Just make sure to protect them so they don't corrode/rust.
If you are running a lot of amperage back through the chassis, you can upgrade the size of the strap running from the battery negative post to the body.

I realize it's just the way it is, but i really don't like the idea of power being on the coax, isn't there a way of isolating it?
I understand the body is part of the electrical system (the negative) for most vehicles, but with an antenna mount that makes the roof a ground plane, makes it also a 12 volt source it just doesn't sit right with me.

Thanks
Joel

 

[mmckenna]

I realize it's just the way it is, but i really don't like the idea of power being on the coax, isn't there a way of isolating it?
I understand the body is part of the electrical system (the negative) for most vehicles, but with an antenna mount that makes the roof a ground plane, makes it also a 12 volt source it just doesn't sit right with me.

Thanks
Joel

No, it's not a 12 volt source.
And an RF ground plane and DC ground are not necessarily the same thing. In your scenario, they are, since the roof sheet metal is part of the vehicle.

Ideally, the roof sheet metal, vehicle body, coax shield and radio chassis should all be at the exact same potential. There should not be any DC current flow on the coax shield. If there is, there's a serious issue with the vehicle electrical system.

 

[TailGator911]

I still have my Dad's grounding board boxed up out in the barn. A 3-ft red cypress board with wingnut connectors on a common copper busbar that grounded his whole desk to an 8-ft rod outside. Another board with a line of mounted Gerber baby food jars to secure his antenna leads during thunderstorms. Pretty cool way of doing things back then. The art of complex simplicity. Sorry, all this talk of grounding connections made me wax nostalgic here. Back to your regularly scheduled programming.